Whole situation started when reddit closed a few hateful subreddits (r/fatpeoplehate, and a few racist ones as well); a very vocal backlash came from the contingent of reddit that believes the admins have no right to 'regulate free speech'. The site was brigaded and flooded with anti-Pao posts (who they saw as their villain) which then turned to racist 'Chairman Pao' posts, posts with her and a nazi flag, etc.
After a while this calmed down.
A week ago reddit fired/let go Victoria, who was the liaison for hundreds of celebrities and reddit, often transcribing entire IAmAs (community interviews). Victoria's departure was immediate and caused a lot of planned IAmAs to be postponed or canceled, since she was the go-between (and in some cases the only point of contact).
A few major moderators were angry and posted about their displeasure at Victoria's departure and the general lack of interface admins have with moderators. This snowballed in to a 'blackout' of many major subreddits for about a day (longer for a few of the smaller ones). One of the admins posted a 'Popcorn tastes good...' comment when people asked him what he thought of the anger; which fanned the flames. The major protests died down after about a day or two, but a few subreddits spawned for the specific purpose of continuing the protest and to oust Pao. These people brigaded most posts about Pao and promoted the petition link calling for her removal. The anti-Pao rhetoric continued at full force (with the usual racist 'Chairman Pao' meme, nazi flags, posts of her photo to a subreddit called 'punchablefaces').
In summary: Pao and admins were wrong to not communicated with the moderators more, especially when it came to Victoria; the original protest had legitimate legs but then devolved in to the same 4chan-esque bile that happens any time reddit makes some sort of administrative move. That awful bile of protest is what kept the flames going which led to Pao stepping down.